This invention relates to door locking apparatus.
It is known to provide electrically operated door locking apparatus in which an elongate lock bolt is moved longitudinally between retracted and extended positions by solenoid action and to provide in such apparatus a dead-locking element which can also be moved by solenoid action between a dead locking position in which it engages the lock bolt to hold the lock bolt in the extended position and a withdrawn, bolt freeing position. Apparatus of this type is satisfactory for many purposes and has particular application where it is desirable to be able to lock and unlock the door from a remote location. However, conventional locking apparatus of this type will usually remain in a locked condition in the event that there is a failure of the power supply to the door and in some applications this can contravene safety requirements for emergency situations. On the other hand, a lock which opened automatically in the event of power failure would not be satisfactory from the standpoint of security. The present invention provides a locking apparatus including an electrically operated lock bolt and which ensures that the door will remain locked in the event of a power failure but which nevertheless allows the door to be opened from one side in an emergency situation without application of electrical power.
The apparatus of the present invention may also include a manually operable latch mechanism in addition to the electrically operated lock bolt to enable a door installation in which both entry and exit through the door is achieved by operation of the latch mechanism but is normally conditional upon prior electrically powered withdrawal of the lock bolt and in the event of power failure entry through the door is prevented but emergency exit is permitted by manual actuation from the inside of the door.